RbC 24 CsC 24
B.5 Conclusion
Hydrogen sorption studies were performed on the ScH2 + 2 LiBH4 system, identified by first-principle calculations as having favorable thermodynamics. Our experimental re- sults demonstrate that H2 desorption is consistent only with independent decomposition of LiBH4. Extensive spectroscopic characterization (XRD, MAS NMR, Raman) failed to detect the ScB2 product of the destabilization reaction. Due to the stability of ScH2 and ScB2, activation barriers in both directions appear to inhibit the predicted reaction at tem-
peratures below 450°C. Sluggish kinetics mean that the destabilization reaction is unfa- vorable compared to competing reactions such as the independent decomposition of LiBH4. Application of a H2 pressure of∼900 bar to a heated ScB2+ 2 LiH mixture was found to yield a minimal amount (i.e., ∼ 3 mol%) of the desired LiBH4 phase. Furthermore, our findings suggest that the ball-milled LiBH4-ScH2 mixture segregates back into LiBH4-rich and ScB2-rich phases, due to the melting of LiBH4. There was no indication that TiCl3 assisted the destabilization reaction, although there was an improvement in the desorption kinetics.
Bibliography
[1] S. Studer, S. Stucki, and J. D. Speight. Hydrogen as a fuel. In A. Z¨uttel, A. Borgschulte, and L. Schlapbach, editors, Hydrogen as a Future Energy Carrier.
Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2008.
[2] A. Z¨uttel. Hydrogen storage materials. Naturwissenchaften, 91:157–172, 2004.
[3] C. Read, G. Thomas, G. Ordaz, and S. Satyapal. U.S. Department of Energy’s system targets for on-board vehicular hydrogen storage. Material Matters, 2(2):3–4, 2007. Material Matters is a publication of Aldrich Chemical Co., Inc.
[4] S. Satyapal, J. Petrovic, C. Read, G. Thomas, and G. Ordaz. The US Department of Energy’s National Hydrogen Storage Project: Progress towards meeting hydrogen- powered vehicle requirements. Catalysis Today, 120(3-4):246–256, 2007.
[5] S. K. Bhatia and A. L. Myers. Optimum conditions for adsorptive storage. Langmuir, 22:1688, 2006.
[6] F. Rouquerol, J. Rouquerol, and K. Sing. Adsorption by Powders and Porous Solids.
Academic Press, London, 1999.
[7] N. Stetson. (Private communication).
[8] J. K. Johnson and M. W. Cole. Hydrogen adsorption in single-walled carbon nan- otubes. In E. J. Bottani and J. M. D. Tasc´on, editors,Adsorption by Carbons, chap- ter 15, pages 369–401. Elsevier, 2008.
[9] V. A. Parsegian. Van der Waals Forces. Cambridge University Press, New York, 2006.
[10] R. Lochan and M. Head-Gordon. Computational studies of molecular hydrogen bind- ing affinities: The role of dispersion forces, electrostatics, and orbital interactions.
Phys. Chem. Chem. Phys., 8:1357–1370, 2006.
[11] G. J. Kubas. Fundamental of H2 binding and reactivity on transition metals underly- ing hydrogenase function and H2production and storage. Chem. Rev., 107:4152–4205, 2007.
[12] W. Zhou and T. Yildirim. Nature and tunability of enhanced hydrogen binding in metal-organic frameworks with exposed transition metal sites. J. Phys. Chem. C Lett., 112:8132–8135, 2008.
[13] A. C. Dillon and M. J. Heben. Hydrogen storage using carbon adsorbents: past, present and future. Appl. Phys. A, 72:133, 2001.
[14] R. Str¨obel, J. Garche, P. T. Moseley, L. J¨orissen, and G. Wolf. Hydrogen storage by carbon materials. J. Power Sources, 159:781–801, 2006.
[15] E. L. Pace and A. R. Siebert. Heat of adsorption of parahydrogen and orthodeuterium on Graphon. J. Phys. Chem., 63:1398–1400, 1959.
walled carbon nanotubes and idealized carbon slit pores. J. Chem. Phys., 110(1):577, 1999.
[17] M. Rzepka, P. Lamp, and M. A. de la Casa-Lillo. Physisorption of hydrogen on microporous carbon and carbon nanotubes. J. Phys. Chem. B, 102:10894–10898, 1998.
[18] S. Patchkovskii and T. Heine. Evaluation of the adsorption free energy of light guest molecules in nanoporous host strutures. Phys. Chem. Chem. Phys., 9:2697–2705, 2007.
[19] M. G. Nijkamp, J. E. M. J. Raaymakers, A. J. van Dillen, and K. P. de Jong. Hydrogen storage using physisorption—materials demands. Appl. Phys. A, 72:619–623, 2001.
[20] B. Panella, M. Hirscher, and S. Roth. Hydrogen adsorption in different carbon nanos- tructures. Carbon, 43:2209–2214, 2005.
[21] F. S. Baker, C. E. Miller, A. J. Repik, and E. D. Tolles. Activated Carbon. In Kirk- Othmer Encyclopedia of Chemical Technology, volume 4, page 741. John Wiley and Sons, 2003.
[22] M. Felderhoff, C. Weidenthaler, R. von Helmolt, and U. Eberle. Hydrogen storage:
The remaining scientific and technological challenges. Phys. Chem. Chem. Phys., 9:2643–2653, 2007.
[23] S. H. Jhung, J. W. Yoon, J. S. Lee, and J.-S. Chang. Low-temperature adsorp- tion/storage of hydrogen on FAU, MFI, and MOR zeolites with various Si/Al ratios:
Effect of electrostatic field and pore structures.Chem. Eur. J., 13(S):6502–6507, 2007.
[24] A. V. A. Kumar, H. Jobic, and S. Bhatia. Quantum effects of adsorption and diffusion of hydrogen and deuterium in microporous materials. J. Phys. Chem. B, 110:16666–
16671, 2006.
[25] N. L. Rosi, J. Eckert, M. Eddaoudi, D. T. Vodak, J. Kim, M. O’Keeffe, and O. M.
Yaghi. Hydrogen storage in microporous metal-organic frameworks.Science, 300:1127, 2003.
[26] H. K. Chae, D. Y. S.-P., J. Kim, Y. Go, M. Eddaoudi, A. J. Matzger, M. O’Keeffe, and O. M. Yaghi. A route to high surface area porosity and inclusion of large molecules in crystals. Nature, 427:523–527, 2004.
[27] H. Furukawa, M. A. Miller, and O. M. Yaghi. Independent verification of the satu- ration hydrogen uptake in MOF-177 and establishment of a benchmark for hydrogen adsorption in metal-organic frameworks. J. Mater. Chem., 17:3197–3204, 2007.
[28] M. Dincˇa, A. Dailly, Y. Liu, C. M. Brown, D. A. Neumann, and J. R. Long. Hydrogen storage in a microporous metal-organic framework with exposed Mn2+ coordination site. J. Am. Chem. Soc., 126:16876–16883, 2006.
[29] Craig M. Brown, Yun Liu, Taner Yildirim, Vanessa K Peterson, and Cameron J Kepert. Hydrogen adsorption in HKUST-1: a combined inelastic neutron scattering and first-principles study. Nanotechnology, 20:204025, 2009.
[30] Y. Liu, H. Kabbour, C. M. Brown, D. A. Neumann, and C. C. Ahn. Increasing the density of adsorbed hydrogen with coordinatively unsaturated metal center in metal-organic frameworks. Langmuir, 24:4772–4777, 2008.
on carbon nanostructures. Appl. Phys. A, 78:941–946, 2004.
[32] N. Texier-Mandoki, J. Dentzer, T. Piquero, S. Saadallah, P. David, and C. Vix- Guterl. Hydrogen storage in activated carbon materials: Role of the nanoporous texture. Carbon, 42:2744–2747, 2004.
[33] P. B´enard and R. Chahine. Storage of hydrogen by physisorption on carbon and nanostructured materials. Scr. Mater., 56:803–808, 2007.
[34] A. Z¨uttel, P. Sudan, Ph. Mauron, T. Kiyobayashi, Ch. Emmenegger, and L. Schlap- bach. Hydrogen storage in carbon nanostructures.Int. J. Hydrogen Energy, 27(2):203–
212, 2002.
[35] E. Poirier, R. Chahine, and T. K. Bose. Hydrogen adsorption in carbon nanostruc- tures. Int. J. Hydrogen Energy, 26:831–835, 2001.
[36] Y. Zhao, Y.-H. Kim, A. C. Dillon, M. J. Heben, and S. B. Zhang. Hydrogen storage in novel organometallic buckyballs. Phys. Rev. Lett., 94(15):155504, Apr 2005.
[37] T. Yildirim, J. ´I˜niguez, and S. Ciraci. Molecular and dissociative adsorption of multiple hydrogen molecules on transition metal decorated C60. Phys. Rev. B, 72(15):153403, Oct 2005.
[38] I. Cabria, M. J. L´opez, and J. A. Alonso. Hydrogen storage in pure and Li-doped carbon nanopores: Combined effects of concavity and doping. J. Chem. Phys., 128(14):144704, 2008.